(a) Field of the Invention
This invention pertains generally to the field of automated drawing apparatus and, more particularly, to cam driven drawing devices such as pantographs.
(b) Statement of the Prior Art
Various cam driven devices for drawing curves are known. Most pertinent to this invention are U.S. Pat. No. 3,444,623 issued to Wolf on May 20, 1969 for a drawing toy and U.S. Pat. No. 3,834,027 issued to Amelon on Sept. 10, 1974, for a device for testing cam designs.
The Wolf device uses a pair of cam followers to drive a pair of crossed, spring loaded oscillating arms.
The arms move independently of each other, the motion being combined at the scribing means which moves along crossed slots in the arms, the crossing point determining the position of the scriber. This device suffers from severe drawbacks due to the limited sweep of arms and the fact that the path of the scriber is not a linear transformation of the cam patterns due to the pivotal mounting of the arms. That is, the oscillatory motion, rather than a linear one, of the cam followers introduces an element of distortion into the system.
Amelon attempts to correct the aforementioned deficiency by providing a pair of linearly movable cam followers. However, as in Wolf, the two cam followers move independently of each other and their motion is combined at the writing pen by a yoke arrangement which adds needlessly to the complexity and cost of the device.